Carlos Armendariz, Jorge Tamayo, Ji Chang | Carnegie Mellon ECE Capstone, Spring 2022
This week, I did the final presentation.
I also drew the letters onto the keyboard with a pen. The only one I couldn’t do was Spacebar, because I drew the letters in a strange order and I couldn’t add the spacebar without smudging. I also started on the poster, but did not finish.
This week was a presentation week.
Ji drew the letters onto the keyboard. Since laser cutting might damage the keys or might otherwise be imprecise, we used a pen. To prevent the ink from rubbing off, we placed scotch tape over the keys as a temporary measure. This would especially be important because testers would have hand sanitizer.
Jorge tested the mouse, and suggested adding a block on the bottom to make it more comfortable. It otherwise worked.
This week, I researched keyboard layouts for the one-handed keyboard. Since qwerty is rather arbitrary, I went with what looked like the closest thing to what we wanted: right-handed Dvorak.
Here is my keyboard layout. I included notes.
Over the weekend, we finalized the keyboard design. I helped mount the base and added rubber tape, allowing the keyguard to rest on top and prevent it from slipping. We also worked on the mouse mount, and I found a strap to attach to the base.
Since we have the presentation, I’m doing that and writing the powerpoint. We’re trying to finish the keyboard so we can do some proper testing before we can report the tests.
This week was rough, since we were all sick with something different. But we did get stuff done.
This week, I looked at potential keyboard layouts. At first, I figured we could sort the most common letters, but then I realized that it would be better if we could find a setup that was already known: Dvorak. QWERTY is designed rather arbitrarily, so I figured that the ergonomically designed Dvorak would work better.
There is already a setup for right-handed Dvorak, so I figured that I could adapt it to our current keyboard.
I am a bit worried that there might be more keys than characters; while we can get some to double up, I’m worried that the hold shift toggle key never showed up in the design.
We worked on the mouse on Monday.
My teammates are working on getting the pi to approve a mouse click, and mouse motions.
We’re looking into taking apart a mouse and then making a new chassis. I’m looking into other ways to operate a mouse with your foot. Actually, we’re now looking into joysticks.
I tried using my computer touchpad with my foot. I could move it, but it didn’t respond well to upward motions and I had trouble with fine movements. Lifting my leg for a long period of time also tired me. So we’re not going to use a touchpad.
In general, mouse sensitivity would have to be reduced, since our feet aren’t as precise as our fingers. We should also include the option to have a normal, hand-operated mouse as a backup. I guess that’s more of a number of USB ports than anything else.
I now think that a joystick is the best way to operate a mouse with your foot. The circle pad on the 3DS looks like the best, since it slides and is concave, but we can’t get a larger version.
Since we already know how to make buttons, we could do a d-pad, with four buttons.
Dance Dance Revolution pad, if smaller.
Since reducing mouse sensitivity would make mouse movement slower, I had thought that holding the stick/key/pad/whatever would gradually speed things up. Then I remembered that hold key presses were the most common error, so we shouldn’t do that.
On Wednesday, Jorge and I soldered the diodes to the board.
This week, we discussed the mouse setup. We were primarily focusing on the keyboard, so we had neglected the mouse design. The mouse will be foot-operated, and the clicks will be on the keyboard.
I proposed looking at larger touchpad peripherals, and placing them on the floor. To ensure that only the more dexterous foot can interact with the keyboard, we proposed that the more functional foot is wearing a sock treated with the cloth that can be used on touchpads, and the other foot is wearing a normal sock. This might cause some problems in hot weather, though. The team accepted that this is a possibility, but we did not finalize the design.
This is the link to the trackpad. This is the largest one we could find, at 6*4 inches.
Once we get the PCB, I want to solder them.
Due to the ethics seminar, we could not do much on Wednesday. We did discuss briefly how our project would potentially cause harm. On one hand, it is a ‘better’ keyboard and keyboards already exist. On the other, Social Media is just a better messaging board. We concluded that by giving some people easier access to services that already exist, we could not cause much harm. We also discussed how a cheaper accessibility keyboard may reduce the job opportunities for stenographers, but there are plenty of other jobs other than typing for the impaired.
We also discussed biases. As a team of able-bodied designers, we need to learn from people with cerebral palsy and what they want in a keyboard/mouse set, and not just what we think they want. We reached out to find people with cerebral palsy and are currently awaiting a response.
On Monday, we were still awaiting the shipment of diodes. I searched for key switches for keyboards (the things you press). We went with linear key switches, the simplest and most common type of key switch.
This is the link to the keys we plan on purchasing. We chose Gateron Ink Black switches because they are relatively inexpensive and have consistently been rated as having a ‘smooth’ feel. I was concerned about the mention of lubricating the keys, but apparently it does not particularly matter for people who do not already construct mechanical keyboards. I had considered the silent version of the keys, but they are more expensive and seem to require more force to operate.
https://divinikey.com/products/gateron-ink-v2-switches?variant=32067927048257
Before spring break, we tried making a better prototype. We did not fully understand how matrix scanning worked, so we assembled a new prototype. This did not work, and upon closer inspection we learned that our diodes were not the right type.
The scanning matrix works by quickly cycling through each column, such that the selected column is pulled to digital low and all other columns are at digital high. It then checks which rows have been pulled low from the switches.
Here is a smaller scale version of the switch.
When we tried making the circuit, we failed because on closer inspection, we had the wrong kind of diode. We used LEDs, which on average drops 1.7 to 2 volts, which would mean that a row with a closed circuit would drop from 3.3 volts to 1.7 volts, which is still a digital high. We are now trying to find diodes with a lower voltage drop, around .3 volts, so that row can be pulled down to a voltage low. We have just ordered a new set of these diodes and are awaiting supplies.
We then moved on to testing the software without the diodes, which helped, but we had the expected ghosting issue. But since the ghosting only happened when multiple columns were on at a time, the circuit and software seems to work and should still work when we add the right diodes.
When it comes to making the PCB, we ran into issues because our board went over the maximum dimensions that Eagle free would allow, so we needed a proper Eagle education license. This was an annoying delay but I (Jorge) submitted my enrollment documentation and the license was supplied the next day. It was a minimal delay, and instead of getting the PCB design finished on Wednesday I got it done Friday. Next steps would be to revise it a little and then decide on a board manufacturer and order it some time next week.
Here below is the board PCB layout
[Note: More specifics on the design in Jorge’s personal status report]
Carlos is also going to reach out to CLASS this week. An organization which the professor in HCI recommended to put us in contact with someone with Spastic Hemiplegia.
As stated on the team report, we made the prototype board, only to run into a wall when we didn’t have the right diodes. We then moved on to the assigned ethics writeup, which we did during class.
I also proposed a way to make the board more durable: wrap the bottom and sides in adhesive rubber strips, and weigh down the bottom so that it would fall down on the rubber instead of the top. We plan to use an extra board to test durability.
This week we were doing the design report, both writing the report and slides, so not a lot got done on the design front. We’re still on track.
I contributed by writing the introduction and editing the use case. I also started on the Architecture and Trade-off sections.